THE TRASH CAN FURNACE

The basic components for this furnace is a common 15 gal galvanized trash can, a cardboard form, and some pieces of wood for supports. A suitable piece of pipe for what ever burner you use will also be needed. In this furnace, I used a piece of 2" iron pipe, which allow a burner of up to 1 1/2" in diameter to be used.. All items are readily available in home builder or hardware stores.

Trash can with inner chamber form in place. The inner form is just a cardboard tube, such as is found in home builder supply stores that is used for forming concrete. My form was a 9" tube, but I slit it and reduced it to 7 1/2" in diameter. The form needs to be held securely in place so it will not move when you cast the refractory. The basic procedure for casting the refractory is to mix the material as per instructions, which will make a material with the consistency of a stiff cookie mix. Place a layer of the material in the form, and tamp with a wooden 2 x 2. Tamping packs and ensures that you do not get any voids, which would diminish your insulating ability. Place more material in form, and tamp again. Repeat until the form is completely full. Remember, follow the mixing directions for your material. Usually less water is better.

You will notice that there is a steel pipe entering the can from the bottom left. This is just an ordinary piece of 2" steel pipe, which enters through the side of the can and into the inner chamber. It is in this tube that you place your burner. The three bolts seen towards the left end of the tube is used to fasten and adjust your burner assembly in the tube. This tube just happens to be 10" O.A.L.. The tube is angled towards the chamber wall, but is horizontal to the ground. This enables the flame from the burner to sort of swirl around the crucible. The flame goes around the wall and the side of the crucible then out the vent in the lid. This also saves a lot of wear and tear on your crucible, by not having it directly in the path of the flame. You also want to position this burner mounting tube so it will allow the burner flame to enter the chamber a contact the lower 1/3 of the crucible.

The lid pictured above is merely a band of 14 ga. 4" flat iron. Regular galvanized sheet metal of 26 ga. can be used to fabricate this lid. The center form is nothing more than a piece of cardboard tube from a roll of carpet, 4" in diameter. When cast with refractory, this lid will weigh in the neighborhood of 60 pounds, so handles are a must. I attached small "L" shaped brackets around the inside circumference of the lid with a spot welder. Rivets, bolts etc will also do, or you can just drill holes and thread the wire used to re-inforce the refractory in place. I placed my re-enforcing mesh 2 1/2" from the bottom of the band. Of course the center form is centered. Its important to cast the lid on a good and flat surface as it must fit pretty close to the top of the trash can when in use. I placed a piece of plastic on the concrete floor. I just happened to get a bunch of 5' x 5' x 3/16" thick sheets from the local Sports Authority store when they changed out their in store displays.

Another view of both lid and furnace forms.

 

View of the furnace after the refractory was cast and tamped. The top needs to be fairly smooth to make a good seal with the lid. Refractory actually entrains air pockets in its process of curing, which further adds to its insulating ability. I used a hot melt glue gun to seal up the opening that I made for the burner mount tube, so it did not leak while the refractory was curing.

Both the furnace body and lid has been cast, so now its just a matter of time for it to harden, so its the perfect time to build the burner and accessories that will be needed.

 

THE BURNER

The burner I used is called the Monster Burner. It is made entirely of common plumbing fittings. Rupert Wenig, designed this particular burner and I must say, it is simple and works like a champ. I designed and built the air choke assembly and simply screwed it to the back of the reducing bell. An air choke is necessary to make more precise adjustments of your air to fuel mix to get the most out of your burner. This burner is quiet, and very efficient. To see a schematic of this burner click here.

 

I won't get into the details here on building the burner, but if your interested, you can find a drawing of this burner and many others at Ron Reils web site. His site has a wealth of information on forges and foundries. Take me to the MONSTER BURNER.

You will also need to read all the associated links under the Monster Burner to get the fuel jetting size etc. The Foundry Melt Logs are especially interesting and impressive.

Here is a side view of the burner on its initial run.

 

The device on the end of the burner tube is called a flare. It is necessary to install a flare on the burner if it is run outside of a furnace. Due to the design of this burner, air is induced at the rear and increased in velocity as it is mixed with propane gas as it travels down the tube. It is traveling at such speed that it will blow itself out as it leaves the end of the tube. A flare reduces the fuel/air mix down to a speed that enables it to burn at the end of the tube instead of being blown out. Once tuned properly the flare is removed and the burner is inserted into the furnace burner mounting tube. For more information on burner flares and how to make them visit the Lionel Oliver at his Lab. Lionel has a lot of unique and interesting information on metal casting and numerous other projects on his website.

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